1. Technical Field
This disclosure relates generally to integrated circuits that include a plurality of fuses wherein at least one of the fuses is intentionally blown by, for example, application of laser energy. More particularly, a fuse in the integrated circuits described herein having a dielectric layer formed thereon can be blown more efficiently during laser deleting by adding a light absorption layer onto the dielectric layer. Methods for producing such integrated circuits are also described.
2. Background of Related Art
Integrated circuits consist of many, sometimes millions, of individual elements joined together on a chip by electrically conductive interconnects. Typically, the interconnects are formed into stacked interconnected levels of a densely packed semiconductor device which create multi-level or multi-layered schemes known as dual damnascene structures as generally depicted in FIG. 1. Methods for manufacturing a dual damascene structure are known. See, e.g., U.S. Pat. Nos. 5,529,953, 5,602,423 and 5,614,765. Generally, when fabricating integrated circuits with a dual damascene structure, an insulating or dielectric material such as silicon oxide of a semiconductor device will be patterned with several thousand openings to create conductive line openings and via openings. The conductive line and via openings can then be filled with a conductive metal layer, e.g., aluminum, to interconnect the active and/or passive elements of the integrated circuit. The dual damascene structure can also be used for forming multilevel conductive lines of metal, e.g., copper, in insulating layers, e.g., polyimide, of multi-layer substrates on which semiconductor devices can be mounted.
It has been found that the ability to alter interconnects on a chip after standard processing is completed provides great improvement in a chip yield (number of working chips) and chip customization (modifying a chip to perform a specific function). A technique widely practiced in the industry involves using light from a laser to vaporize (blow) segments of interconnects (referred to as fuses), thereby forming an "open" that eliminates the electrical connection originally provided by the interconnect. Usually, these fuses are connected to redundancy circuits, replacing defect word- and/or bit-lines with redundant lines (redundancy activation).
Although this technique of laser deleting has been widely used in an attempt to improve functional yields, fuse flow yields and fuse reliability have been problematic in devices made where a fuse such as, for example, an aluminum fuse, is positioned under a dielectric layer, e.g., TEOS. Specifically, when the application of laser energy to the fuse having the dielectric layer formed thereon, the light from the laser is reflected from the device instead of being absorbed and subsequently converted into heat. Therefore, the fuse is not melted and the laser cannot blow the fuse thereby lowering the efficiency of the fuse blow.
It would be desirable to provide a light absorption layer on top of a dielectric layer covering a fuse to allow light from laser energy to be converted into heat thereby blowing the fuse.